Appearance of water- and oil-repellency by fluorine-containing polymers is attributable to the low surface energy of fluorine atoms. In general, a fluorine-containing (meth)acrylate-based polymer is often used as an active component of water- and oil-repellent.
For performance appearance as a water- and oil-repellent, it is important that water- and oil-repellent particles in the working fluid are uniformly adsorbed to the fiber surface. The zeta (ζ) potential of the fiber surface generally has a negative (anionic) potential, regardless of the type of natural fiber or synthetic fiber. Accordingly, it is necessary that the water- and oil-repellent particles have a moderate positive (cationic) potential. Thereby, stable adsorption occurs on the fiber surface, and stable performance is exhibited.
In contrast, water- and oil-repellent particles having an overly high positive potential may lead to a phenomenon in which many water- and oil-repellent particles are selectively adsorbed at once to the fiber surface having a negative potential, resulting in unstable performance, and uniform adsorption of the water- and oil-repellent particles may be inhibited by repulsion, thereby reducing the performance. Therefore, in water- and oil-repellents used for the treatment of fiber and the like, controlling the surface potential of the water- and oil-repellent particles is also important from the viewpoint of obtaining stable processability.
In order to give a positive (cationic) potential to the particle surface, use of a cationic emulsifier is proposed. For example, Patent Document 1 proposes a process for preparing an aqueous dispersion, the process comprising subjecting a polyfluoroalkyl group-containing (meth)acrylate and a fluorine atom-free polymerizable monomer to an emulsification treatment in the presence of a polypropylene glycol-based compound and a cationic surfactant comprising a quaternary ammonium salt, followed by copolymerization in the presence of a polymerization initiator.
However, in the successive processing of fiber and the like, dyes, chemicals, and the like used in the previous process before dyeing serve as impurities, and they are brought into a processing bath and accumulated therein. Because these impurities are mostly hydrophilic anionic substances, they react with the cationic emulsifier, thereby leading to troubles due to coagulation and sedimentation of the water- and oil-repellent and causing a depression of water- and oil-repellency.
Further, from actual circumstances where various chemicals have been increasingly used in combination in recent years, corresponding to processing purpose of and processing target of fiber and the like, the compatibility of water- and oil-repellents with other chemicals used in combination, that is, chemical stability, is strongly demanded.
Patent Document 2 discloses a water repellent-, oil repellent-, and soil release-processed textile using a water- and oil-repellent and a soil release agent in combination. The soil release agent used herein is a fluorine-containing copolymer comprising a fluorine-based monomer and a hydrophilic group-containing monomer. As examples of the hydrophilic group-containing monomer, Patent Document 2 refers to monomers having an ionic group (i.e., a cationic group or an anionic group) and an unsaturated bond, such as 2-methacryloyloxyethyltrimethylammonium chloride and N,N,N-trimethyl-N-(2-hydroxy-3-methacryloyloxypropyl)ammonium chloride.
In the fluorine-containing copolymer for the soil release agent, the amount of the hydrophilic group-containing monomer is described to be 10 to 80% by weight, preferably 15 to 60% by weight, for example 20 to 50% by weight, based on the total weight of the fluorine-based monomer and the hydrophilic group-containing monomer. In Synthesis Example 2, which shows an example of synthesizing a soil release agent, the following components are used:
Perfluorooctylethyl acrylate60g (60 wt. %)Methoxypolyethyleneglycol methacrylate30g (30 wt. %)2-Hydroxyethyl methacrylate8g (8 wt. %)2-Methacryloyloxyethyltrimethylammonium2g (2 wt. %)chlorideIt is described that the constituents of the obtained copolymer were substantially equal to the composition of the charged monomers.